1. Field of the Invention
The present invention relates to stepladders. More particularly, the present invention relates to the foldable stepladders. Additionally, the present invention relates to stepladders that can be folded so as to be utilized as a single ladder or as an extension ladder.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
Ladders are commonly used as a means for elevating persons to a specified height in order to perform a specified function. The users of ladders will climb a series of steps, or rungs, in order to reach a desired height. Stepladders are ladders in which a first ladder section extends at an acute angle with respect to a second ladder section. The first ladder section will have the steps or rungs thereon. The second ladder section is intended to provide structural support for the leaning of the first ladder section. As such, stepladders can be used in locations where there is no support surface.
Single ladders require the use of an extrinsic support surface. A single ladder includes a pair of side rails and a plurality of steps, or rungs, extending between the pair of side rails. Typically, the bottom of the stepladder will be placed upon an underlying surface. The single ladder will lean at an acute angle with respect to the underlying surface so as to have an upper end resting against the extrinsic surface.
Extension ladders typically consist of a base section and one or more fly sections with each fly section extendable from the preceding section. The term “base section” is used to refer to the lower of two adjacent sections of an extension ladder, from which a fly section is extended upward. The base section may be the section of the ladder onto which the user first climbs. Typically, with extension ladders, the bottom of the extension ladder will reside on an underlying surface while the fly section extends upwardly and outwardly from the base section so as to have an upper end that rests against an extrinsic surface, such as the side of a building. Extension ladders, in the past, extend linearly and do not have outwardly extending supports therefor.
In the United States and most other countries, it is prohibited lean a closed stepladder against a wall or extrinsic surface for use as a single ladder. The reason is twofold. First, a stepladder is designed to be self-supported on four legs so as to distribute the user's weight across four legs instead of two legs. Secondly, when the closed stepladder would lean against the wall, the other ladder section of the ladder can possibly unfold so as to contact the underlying surfaces and possibly upset the first ladder section. This could potentially cause a slip-out event to occur.
Unfortunately, under those circumstances where different ladders are required, the users are required to purchase a stepladder for one set of purposes and a single or extension ladder for other purposes. Often, the proper type of ladder will not be available when the need for such a ladder occurs. As such, a need has developed whereby a stepladder can be adapted for use as a single ladder or as an extension ladder while still being able to handle all ANSI performance standards as both a four-legged stepladder and also the more stringent loading conditions required of a single ladder. In the past, various patents have issued with respect to such stepladders.
An early patent for a folding stepladder is described in U.S. Pat. No. 341,284, issued on May 4, 1886 to T. P. Sharp. This folding ladder has rungs arranged in pairs. The rungs of each pair are arranged one back of the other end near the upper end of the ladder. A pair of ladder sections are hingedly connected together at the upper end thereof so that one ladder section can fold downwardly so as to extend into a generally inverted V-shape configuration with respect to the other ladder section.
U.S. Pat. No. 1,772,213, issued on Aug. 5, 1930 to B. F. Francois, describes a folding stepladder that includes a bridge member, spaced-apart guides mounted on the bridge member, a ladder unit slidably connected to one of the guides and having foldable steps, and a prop unit slidably connected to the other of the guides. The ladder and the prop units include sections hingedly connected to be folded upwardly. The ladder and prop sections are collapsible respectively at diagonally opposite portions of the guides. As such, the folded sections may be folded laterally of each other.
U.S. Pat. No. 2,088,878, issued on Aug. 3, 1937 to G. H. Stogner, describes a foldable stepladder that includes spaced side members and steps. Each of the side members includes pivotally connected sections pivoted at their outer ends to the side members and adapted to be folded in parallel between the side members. A bar connects all of the steps for folding the steps in unison. Hinges connect the supporting legs to the side members at the upper ends of the side members. Braces are pivoted at one end to the supporting legs and of a second end of the sections of the uppermost step so as to transmit movement of the sections of the step to the supporting legs.
U.S. Pat. No. 2,167,157, issued on Jul. 25, 1939 the K. O. Muehlberg, describes a stepladder that includes a ladder member having side rails and a top platform. Supporting legs are foldably connected to the platform. An elongated arm is slidably mounted through a tapered slot in the top platform and normally disposed in an angle to vertical against the side of the supporting leg. The arm is movable in the slot of the platform to a selected position of the projection extending vertically above the platform.
U.S. Pat. No. 2,255,756, issued on Sep. 16, 1940 to J. M. Bigen, shows a folding stepladder that comprises a primary ladder, an auxiliary ladder positioned to move parallel to the primary ladder, and a means that slidably connects the primary and auxiliary ladders together. A brace is provided for the primary ladder. A pivotally mounted transverse bar connects the lower ends of the brace bars. A platform is secured to the upper end of the auxiliary ladder.
U.S. Pat. No. 3,084,760, issued on Apr. 9, 1963 to B. Lamberti, shows a stepladder with folding elements. The stepladder includes a pair of side rails that are fixed together at the upper ends thereof. Foldable rungs extend between each of the side rails. The foldable run can fold so that the side rails can be position in a folded configuration.
U.S. Pat. No. 3,208,553, issued on Sep. 28, 1965 O. Gray, describes a folding ladder in which a first ladder section is hingedly connected at an upper end thereof to a second ladder section. The first and second ladder sections can extend outwardly so as to be aligned longitudinally in end-to-end relationship. The ladders can be fixed in this end-to-end relationship.
U.S. Pat. No. 3,447,632, issued on Jun. 3, 1969 to C. R. Boyd, discloses a folding tripod-type of ladder in which each of the legs can be folded in a compact configuration so as to support a platform at an upper end thereof.
U.S. Pat. No. 3,744,591, issued on Jul. 10, 1963 to R. Lucci et al., discloses a portable stepladder that has a row of steps supported by side posts and a rear post with an upper end that is pivotally connected to the upper end of the stepladder along a horizontal axis. The stepladder and the rear support are longitudinally split into two sections hinged to one another. Each of the hinged connections lies in a common plane so as to allow the stepladder to be folded up to a closed configuration.
U.S. Pat. No. 4,483,415, issued on Nov. 20, 1984 Disston et al., shows a folding stepladder that includes a lower step section and a strut pivotally connected at the upper ends for swinging movement between a collapsed position, one within the other, and a downwardly divergent erected position. The upper section is pivoted to the upper end of the lower step section for swinging movement between a folded position closely overlying the lower step section and an erected position inclining as an extension of the lower step section.
U.S. Pat. No. 7,849,967, issued on Dec. 14, 2010 to Gibson et al., provides a stepladder that includes a longer inclined frame provided with steps coupled to a shorter stabilizer frame provided with rungs for movement relative to the longer inclined frame between an expanded use position and a collapsed storage position. The stepladder also includes a top-step lock-to-lock for in a fixed position relative to the two frames.
It is an object of the present invention to provide a stepladder apparatus that can function both as a stepladder and a single or extension ladder.
It is another object of the present invention provide a stepladder apparatus in which the stepladder apparatus is able to meet all ANSI performance tests as both a four-legged stepladder and as a two-legged single or extension ladder.
It is another object of the present invention to provide a stepladder apparatus which can be folded into a compact configuration.
It is another object the present invention provide a stepladder apparatus in which one ladder section can be locked to the other ladder section when the ladder sections are closed together.
It is a further object of the present invention to provide a stepladder apparatus in which the second ladder section will lock against the first ladder section when in a single ladder or extension ladder configuration.
It is still another object of the present invention to provide a stepladder apparatus that has a ladder top that facilitates the use of the stepladder apparatus against flat surfaces, wall corners, or against round surfaces.
It is still a further object of the present invention provide a stepladder apparatus that avoids the cost for the user associated with purchasing a single ladder, an extension ladder and a stepladder as separate items.
It is still further object of the present invention to provide a stepladder apparatus that automatically locks when the second ladder section is brought against the first ladder section and which requires manual operation in order to release the ladder sections from their locked configuration.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.